Field of the Invention
The invention relates to a device for controlling (driving) capacitive actuators. The invention pertains in particular to the control of fuel injection valves of an internal combustion engine by means of signals fed to a control circuit. The system includes a configuration for producing a high voltage from a DC voltage source, a capacitor, a charging coil, a discharging coil, and at least one charging switch and one discharging switch. The invention also relates to a method for operating the device.
Japanese patent abstract JP 3-199650 A (Patent Abstracts of Japan M-1183, 25 Nov. 1991, vol. 15, No. 463) discloses a circuit for driving a capacitive actuator by means of a control circuit, which has a voltage source for producing a high voltage, a capacitor, a charging coil, a discharging coil as well as a charging switch and a discharging switch. If, as a result of spurious signals, the charging switch and the discharging switch are turned on at the same time, the circuit is isolated from the voltage source.
German published non-prosecuted patent application DE 36 21 541 A1 discloses a device for driving capacitive actuators. The device includes a capacitor that can be charged from a voltage source, a charging coil and a discharging coil. A voltage U.sub.P which can be achieved at the capacitive actuators is limited to a value U.sub.P &lt;2U.sub.B less than two times the output voltage U.sub.B of the voltage source.
That circuit is not suitable for a high voltage supply to capacitive actuators for fuel injection valves of a motor vehicle internal combustion engine, with U.sub.B .apprxeq.15U.sub.B. Higher voltages can be produced in known fashion by means of switched mode power supplies (SMPS).
Because of the dimensions of the coils of the switched mode power supply SMPS (transformer), of the charging coil and of the discharging coil, as well as their weight, problems result when they are placed into a housing specific to a motor vehicle.